Regulation of Bacterial Glycogen Synthesis: Structure-Function Relationship of Adp-Glucose Pyrophosphorylase

Starch is an important source for energy, and it has become a significant resource for bio-fuel production. ADP-glucose pyrophosphorylase is the enzyme that controls the synthesis of starch in plants, and glycogen in bacteria. This regulation is mainly driven by allosteric activators (Fru6P, FBP, and Pyruvate) in bacteria. It has been hypothesized that inter-subunit communications are important for the allosteric effect in this enzyme. Here we show that one specific subunit interface and the interaction between amino acids Arg11 and Asp141 are critical for the regulatory signal in the enzyme from Agrobacterium tumefaciens. Manipulation of this regulatory signal is critical to obtain species with high polysaccharide content used for biotechnological purposes. We have also found the activator (pyruvate) binding site of the ADP-Glc PPase from Agrobacterium tumefaciens. We confirmed that mutation of the residues Lys43 and Gly329 that reside near the pyruvate binding site are important for activation. The produced mutations are either insensitive to pyruvate or are hyper active. According to our analysis, the mutation also affects the binding of the pyruvate molecule. Understanding the control mechanism of this particular enzyme, can give us important insights in to regulating and engineering the enzyme for increased starch production